found this that should help me with setting the HU volume output:
Then I'll adjust the Helix Sensitivity until it clips, then back off to no clip light.
Also found these instructions in my archives:
Tools needed :
Oscilloscope or DD-1 (use 40hz and 1khz )
Sine wave tracks
Start by turning off your amps. Play a 1kHz sine wave recorded at 0 db (full volume). You can download these and burn them to a disc or put them on a thumb drive if your head unit will play them. Connect the oscilloscope to an RCA output on your head unit. Bypass all eq, tone controls, and any other effects the head unit may have. Turn everything off... Now play the sound file and look at the oscilloscope. Turn the receiver up all the way (amps off). If you see the wave start to develop flat lines on the top and bottom, you are clipping and need to turn the head unit down. The point where you get no clipping is the max volume of the head unit. My Kenwood will go to 40 but I got clipping around 38. 37 is the maximum volume I can use and avoid clipping. Repeat this process for both channels.
Do this with a 40hz tone for sub channels. Use the lowest volume of clipping between high sine wave and low and that is now max volume for the head unit.
So if low wave clips at 34 and high wave clips at 37, 33 is now your max volume from the headunit.
Next you need to connect the dayton 408 and do the same thing. Mute all channels (amps still off) and then play only one. Turn your head unit to the maximum volume you determined previously and connect the oscilloscope to one output on the dayton dsp . Ensure all EQ is bypassed on the dayton dsp. But you have some basic crossovers set to protect the speakers. Turn the output gain down about half or so to ensure the dsp doesn't clip and put the master volume at 0db. Now raise the input gain on the DSP for that one channel until you just start to see clipping. Turn it down until it just goes away. This is your max input setting. Do this for the other channel.
***set the above with 1khz tone for mid and tweeter channels, and 40hz tone for sub channels
Next you want to set the outputs of the dayton dsp 408. Pick one channel and connect the oscilloscope to it's RCA output. You've already set the gain on the head unit and the input section of the D408. Now set the output gains the same way. Raise the output slider within the D408 software until you see clipping on that RCA. Now back it down until it goes away. Do this for all your output channels (amps still off).
***set sub output channels with a 40hz tone. And all others outputs with a 1khz tone.
Now you have unity gain from the head unit all the way through the D408. Now it's time to set the gains on the amps. You essentially do the same thing. Provide a 1kHz signal to each speaker, one at a time with the speakers hooked up to give the amp a proper load.
(40hz tone for sub channels)
Connect the oscilloscope to a speaker output on the amp . Turn the amp gain all the way down. Turn the head unit to max volume without clipping. Play the signal and then turn the amp gain up slowly until you start to see clipping. Turn it down until it's clean and then mute the channel and go on to the next one.
When you do this for tweeters, make sure you have a crossover setting enabled within the D408. Put in a high pass at 6kHz or so to provide some speaker protection. The other speakers won't need any crossover. 20kHz is a safe signal to play. Just don't take too long tuning the tweeters. They can overheat if played too long.
Now when you set your levels, you will only turn down channels, not up. Use your SPL meter to find the quietest speaker. Now turn down all the other speakers until you match the level of the weakest. Never boost signal when setting gains this way or you will clip. The system is already at max level and so any tuning should only involve cutting, not boosting. You can boost some individual levels within the EQ as long as the overall signal is not boosted. Tune EQ by cutting the high spots first. Anything that is too loud in the response needs to be cut. Then provide a minimum boost to any weak areas. Ensure your overall signal level doesn't increase to avoid clipping.
